Which type of waves are characterized by being processed without heat and utilize thioglycolic acid as a main ingredient?

The correct answer is cold waves. Cold waves, often referred to as exothermic waves, are unique in their formulation as they primarily utilize thioglycolic acid to achieve hair texture changes. They are specifically designed to create curls and waves in hair without the application of heat. Instead, they work through the chemical action of the solution that penetrates the hair shaft, breaking and reforming disulfide bonds in the hair structure.

Because cold waves do not require heat to activate the chemical process, they are often favored for their ability to create soft, natural-looking waves without the potential damage that heat styling can cause. Thioglycolic acid serves as a reducing agent in this type of wave, making it essential in ensuring the hair is properly curled or textured.

The other types of waves mentioned do not fit this description—acid balanced waves, for instance, are formulated to be gentler and may require heat to process effectively, while alkaline waves are typically characterized by being more alkaline in nature, often needing either some heat or being used at higher pH levels.